A virtual machine (VM) is a software implementation of a machine (i.e. a computer) that executes programs like a physical computer. Software running inside a virtual machine may be limited to the resources and abstractions provided by the virtual machine. Virtualization may allow the sharing of the underlying physical resource between different virtual machines. With virtual machines, multiple operating system (OS) environments, each a VM, can co-exist on the same physical host machine.
One common application of virtual machines is in data centers. Data centers may include facilities to house computer systems and associated components, such as telecommunications and storage systems. Virtual machines may be used in data centers to help manage the use of the data center hardware. For example, instead of dedicating each data center server to a single physical host device, the data center servers may be implemented as virtual machines in which multiple virtual machines are run on a single physical host device. As the computing demands of the data center changes, virtual machines can be dynamically added, removed, or moved between physical hosts.